When lumber drives, in which direction does it tend to shrink the most?

When lumber dries, it tends to shrink the most in width. This phenomenon occurs because the cellular structure of wood is anisotropic, meaning that it exhibits different properties in different directions. Wood fibers run primarily along the length of the board, which significantly influences how wood reacts to changes in moisture content.

As lumber dries, the most significant movement happens across the grain, which is primarily in the width direction. Therefore, when the moisture evaporates, the wood shrinks more noticeably in width compared to length or thickness. This characteristic is particularly important for builders and carpenters to understand, as it affects the stability and fitting of wooden components in construction projects.